Cathode spacers



March 8, 1960 WETMQRE 2,928,018

I CATHODE SPACERS Filed July 7, 1959 //V VE N TOR ARTHUR R. WETMORE A T TORNE Y Unite States Paten CATHODE SPACERS Arthur R. Wetmore, Framingham, Mass., assignor to Raytheon Company, Waltham,'Mass., a corporation of Delaware Application July 7, 1959, Serial No. 825,542

6 Claims. Cl. 313-270 This invention relates generally to cathode structures and, more particularly, to means for spacing, or positioning, cylindrical cathode emitting sleeves in magnetron tubes, or the like.

In conventional magnetron tubes, the cathode emitter is often formed in the shape of a cylindrical sleeve which fits over a cylindrical support and is positionedbetween a pair of end shield assemblies. The cylindrical support is usually fabricated of tungsten material so as to prevent interaction between the thorium impregnated cathode material and the support. It is desirable to space the cathode emitting sleeve at a substantially central position between the end shields and to prevent the emitting sleeve from sliding along the cylindrical cathode support.

ice

. plane of the triangle partially formed by sides 6, 7 and,

8 so as to provide projecting legs. -In addition, free ends 11 and 12 are also bent downwardly'from the plane of the triangle to form additional projected legs, The length of t the tungsten wire is selected so that, when the wire is bent into the desired shape, it fits relatively tightly around a cylindrical cathode support.

Fig.2 shows the cathode spacer of Fig. l as it is used in a cathode assembly. In Fig. 2 there is shown a cylindrical cathode support 13 which, as mentioned above, is conventionally made of rolled tungsten; A pair of end shield assemblies 14, comprising a first cylindrical support 23, a second cylindrical support 24, and end shields 25, are riveted at points 15 to cylindrical cathode support 13. A cathode emitting sleeve is positioned around cathode support 13' between end shield assemblies 14. Cathode emitting sleeve 16 is held between end shields by cathode spacers 5 which correspond to the cathode spacer configuration shown in Fig. 1. As can be easily seen in Fig. 2, the triangular sides of the cathode spacers contact end shields.

In prior art cathode structures, such spacingis often provided by welding tabs to the cylindrical support at each end of the emitting sleeve so that the sleeve is held in place between the tabs. However, since tungsten after heating becomes extremely brittle when it cools down, the welding of these tabs causes the tungsten material tobe weakened at the points of weld. This type of structure often causes difficulty in production line operation since many, cathode structures are lost because of cracking of the cylindrical tungsten support either during the assembly process itself or, thereafter, when the tube is later used. Other prior an devices require relatively elaborate machining methods for providing suitable locking mechanisms to hold the cathode emitting sleeve in place. Such machining methods require added equipment which increases not only the cost of the tubes, but also the time required for assembling the tubes.

This invention describes a means for spacing a cathode between the end shields with a relatively inexpensive structure which is easily fabricated and assembled. In one particular embodiment of the invention, the cathode spacers are formed from pieces of tungsten wire that are formed into substantially triangular shapes. The corners of the triangle are bent downwardly at an angle from the plane of the triangle so as to form legs. These triangular cathode spacers are positioned around the cylindrical tungsten support between the ends of the cathode emitting The the ends of the cathode emitting sleeve. Thus, the tungsten wire spacer holds the emitting sleeve'in a substantially center position between the end shields.

The invention can be most easily described with the help of the drawing in which:

Fig. 1 shows a pictorial view of one specific embodiment of the cathode spacer of the invention; and

Fig. 2 shows a cathode assembly which utilizes the cathode spacers of the invention. 7

In Fig. 1, there is shown a piece of tungsten wire 5 bent into substantially the shape of a triangle having sides 6, 7, and 8. The free ends of the wire are not joined in the bent so as to form substantially equal angles with side 8.

- It is apparent that the cathode spacers ned not be constructed according to the specific configuration shown in V Fig. 1 andutilized in Fig. 2. For example, it is possible to join together the free ends of the tungsten wire so as to form a closed triangular piece. For production simplicity, however, it has been found to be advantageous to eliminate any extra production steps which may be required to join the ends together and, hence, they are usually allowed to remain unjoined. The spacers need not necessarily be triangular in shape, but can be made in any suitable polygonal shape wherein projecting legs can be formed by bending down all or at least some of the corners that are available. The triangular shape has been found to be most efiicient because it is generally easier to fabricate and because, by utilizing the least number of projecting legs,the possibility of undesirable heat drain from the cathode emitting sleeve is reduced.

Other desirable configurations will occur to those in the 'art within the scope of this invention. Hence, the invention is not to be construed as limited to the specific embodiments shown and described herein except as defined by the appended claims. i

What is claimed is 1. Cathode spacing means comprising a substantially polygonally shaped member having a plurality of legs projecting at an angle from the plane of said member.

2. Cathode spacing means comprising a substantially triangularly shaped member having a plurality of legs projecting at an angle from the plane of said member.

3. Cathode spacing means comprising a substantially triangularly shaped member having its corners bent at an angle from the plane of said triangle so as to form projecting legs.

, 4. Cathode spacing means comprising tungsten wire shaped substantially in the form of a triangle having its corners bent so as to form a plurality of legs projecting at an angle from the plane of said triangle.

6. A cathode assembly including cylindricalcathode I support means; a cathode emitting sleeve enclosing a portion of said cylindrical support means; end shields mounted on said cylindrical support means adjacent each end of said cathode emitting sleeve; cathode spacing means.

positioned between the ends of said cathode emitting sleeve and said end shields for holding said cathode emitting sleeve between said end shields, each of said cathode spacing means comprising a triangularly shaped member having its corners bent to form projecting legs, said legs contacting said end shields and the sides of said triangularly References Cited in the file of this patent UNITED STATES PATENTS Clark et a1. Jan. 7, 1947 Varian July 22, 1952 

